There are various types of radio communication schemes for mobile telephones, such as Global System for Mobile Communications (GSM) and CDMA, and communication schemes between communication carriers may differ. Communication schemes differ among terminal types, e.g., international roaming terminals and non-carrier-restricted simlock free terminals, and recently communication schemes even differ for the same carrier depending on the service provided. Consequently, terminals that can support more than one communication scheme are appearing.
The simplest method of supporting multiple communication schemes by a single terminal is to equip the terminal with processing circuits, such as baseband units, respectively corresponding each scheme that is to be supported. A terminal equipped with multiple processing circuits in this manner is called a multimode terminal. Techniques for efficiently determining the communication scheme to be used in such multimode terminals have been disclosed (for example, refer to Japanese Laid-Open Patent Publication No. 2009-147956).
Without disposing dedicated processing circuits for each communication scheme like the multimode terminal above, software defined radio (SDR) terminals use a processor to perform the digital processing portion of radio communications processing. SDR terminals have an advantage in that even if the number of supported communication schemes increases, the additional communication schemes can be accommodated without increases in the size of the circuit for digital processing in the processor, etc. because a common processor is used for processing under the different communication schemes.
Further, a technology has been disclosed in which a single terminal concurrently communicates with multiple base stations, thereby improving communication performance. For example, a technique has been disclosed in which multiple SDR communications units (digital baseband units) are disposed and communication is performed concurrently with plural counterparts (for example, refer to Japanese Laid-Open Patent Publication No. 2011-9964).
Nonetheless, with the technology recited in Japanese Laid-Open Patent Publication No. 2009-147956, dedicated processing circuits such as baseband units have to be disposed for each communication scheme and consequently, the size of the processing circuit increases according to the number of communication schemes and corresponding installation space is necessary. Further, with the technology recited in Japanese Laid-Open Patent Publication No. 2011-9964, although processing for different communication schemes can be performed commonly using a processor by a SDR communications unit, to concurrently communicate with multiple base stations, SDR digital baseband units equivalent in number to the number of concurrent communication counterparts are necessary. Consequently, the size of the circuit increases and corresponding installation space is necessary.
Although improved communication speed can be facilitated by a terminal concurrently communicating with multiple base stations, no technique has been proposed that includes different communication methods and obtains the optimal communication method(s) and the number of communications to be performed concurrently. Here, communications capability (communication speed) differs according to communication scheme, and the processing capability demanded of the processor differs. To cope with changes in the communication state with a base station consequent to movement, etc., the terminal has to perform high-speed communication under a communication state that is continually favorable.
Further, since the terminal is compact and batter-operated for portability, reductions in the number of processing circuits and installation space, as well as facilitation of low power consumption are necessary. However, with the conventional technologies, the processing described above to be performed efficiently and using the least amount of resources possible, i.e., communication by communication schemes among the communication schemes and enabling concurrent communication cannot be performed.